I know that the scene with the kids in the finale of How I Met Your Mother had all been recorded a while back as a way to make sure they looked the same throughout the series, and I know the ending had been decided a lot sooner than some other parts of the series. However, there are scenes that give us flashbacks in which the actors actually look younger than they do in the rest of the episode. And some of these scenes are slowly completed as the years go by.
Take Barney and Ted's first meeting scene. When there is a first appearance by that scene they actually look like they would the year they met. And than in later episodes (and seasons) the scene is completed with other, shorter, shorter scenes in which Ted and Barney still look about the same age they did when the scene first came up.
Were those kinds of scenes actually recorded in the earlier seasons of the show or do they use make up only to make it seem like the past?
I would have guessed make up, but because of the fact with the kids scene I thought I might be wrong.